Products using rechargeable batteries go on increasing. Rechargeable batteries are much used in portable devices such as cell phones and laptop computers. Rechargeable batteries are paid attention to also as large power sources for electric cars.
Electrodes of rechargeable batteries are constituted, for example, of a current collector formed of a metal material such as copper or aluminum, and an active substance layer bound on the current collector. The active substance layer generally contains a binder for electrodes for binding an active substance on the current collector. In recent years, as the binder for electrodes, polyacrylic acid, which is an inexpensive polymer compound, has been utilized. For example, Patent Document 1 discloses a binder for electrodes containing a polyacrylic acid lithium salt or a polyacrylic acid sodium salt. Patent Document 2 discloses a binder for electrodes containing a polyacrylic acid and a polyethyleneimine. Patent Document 3 discloses a binder for electrodes containing a polyacrylic acid and an amine compound.